DESCRIPTION: (Verbatim from the Applicant's Abstract) Defective chloride transport in epithelial cells results from mutations in the cystic fibrosis transport regulator (CFTR). A potential approach for treatment of cystic fibrosis (CF) would be to restore chloride transport to airway epithelial cells. In this pursuit, a series of water-soluble anion-conducting peptides capable of spontaneous insertion into epithelial cell membranes have been synthesized. This family of peptides is modeled after the pore-forming M2 transmembrane segment of a anion-selective channel, the brain glycine receptor (M2GlyR). To enhance the aqueous solubility of the hydrophobic M2GlyR sequence, various numbers of lysine residues have been added to either the C- or N- terminus. These peptides are able to increase short-circuit currents and water transport across epithelial cells. The specific aims of the proposed research are to further characterize, biophysically, the lead compound CK4-M2GlyR as well as variants of the M2GlyR sequence that are modified by: i) additions of various ionic groups to the C- or N-terminus; ii) replacement or rearrangement of transmembrane residues; iii) changing chirality by using all D amino acids. The resulting peptides will be evaluated in terms of properties essential for a potential therapeutic agent for CF including aqueous solubility, anion selectivity, membrane affinity, ability to enhance chloride transport in whole cells, long half-life and low cytotoxicity. The long-range goals of this project are to use molecular modeling to define the relationships between structure and function for the M2GlyR family of peptides and to design an optimized anion-conducting peptide. This compound will then be evaluated for its effects on the function of normal and CF airway epithelial cells from mouse and human sources. This in depth structure-activity study will also increase our knowledge about peptide-lipid interactions in general, an area of research that becomes increasingly important as more naturally occurring peptides are found to have channel-forming activity.